If you are just starting use of OpenCPN, do not concern yourself with this aspect. Get your GPS working and Install Charts first.
OpenCPN is conversant in NMEA0183, but not NMEA2000. Therefore to connect OpenCPN to newer instruments a converter will be needed. It is worthwhile to review the OpenCPN Manual, Supplementary Hardware Section before purchasing anything. To connect your instruments (B&G, Raymarine, Garmin, etc) there are a number of options available. Alternatives are:
1. If you have a recent B&G chartplotter with WiFi, you can configure it as a Wifi hotspot and send NMEA 183 data to OpenCPN. The B&G chartplotter acts as a NMEA 2000 to NMEA 183 gateway. Note that there are other less expensive or more capable hardware devices than these Artisense devices mentioned in Supplementary Software.
2. Review the many alternatives for connecting your vessels instruments here in Supplementary Hardware Section
3. An Actisense NGW-1 (USB) or W2K-1 (WiFi) convert NMEA 2000 to NMEA 183. Actisense NGT-1 does not convert NMEA2000 to NMEA0183 to work with OpenCPN.
4. If you have a Actisense NGT-1 exchange it or investigate Signal-K Server which does support the NGT-1, and can convert NMEA 2000 data to either Signal-K or NMEA 183, both of which OpenCPN supports. We do not have details for Windows about this setup yet.
5. Consider the TwoCan plugin for OpenCPN, which supports a number of CAN Bus adapters on Windows and converts NMEA 2000 to NMEA 183. This would require you to purchase one of the inexpensive CAN Bus adapters that TwoCan supports.